Note the difference between the endothelial cells with oblong, pale nuclei (arrowheads) and the small lymphocytes with round, dark nuclei (arrows) traversing by diapedesis through the HEVs (HA21). There are a large number of lymphocytes beneath the basement membrane of the HEV. The other cell types are reticular cells/fibroblasts and dendritic cells, but these cannot easily be distinguished.